| 摘要 |
<p>Particle-optical rotationally-symmetrical lenses inevitably exhibit spherical and chromatic aberration. These lens aberrations usually determine the limit of the resolution of the known particle-optical apparatus. Said lens aberrations cannot be eliminated by compensation by means of rotationally-symmetrical fields. In order to enhance the resolution of particle-optical apparatus nevertheless, it is proposed to reduce said lens aberrations by means of a 'Wien-type' corrector. Such a configuration must satisfy very severe requirements as regards manufacturing precision, mechanical stability (inter alia with a view to thermal drift), alignment of the various elements relative to one another, and stability of the electric currents and voltages for the excitation of the electric and magnetic poles. Because the known correction device is composed of a number of separate components, it is extremely difficult to satisfy the requirements as regards manufacturing precision, mechanical stability and alignment simultaneously for all of these components. In the corrector in accordance with the invention said requirements in respect of mechanical stability and precision are satisfied in a simpler manner in that the pole faces determining hexapole fields are arranged adjacent one another without other particle-optical elements being arranged therebetween.</p> |
